Pressurized fluid systems are typically provided with pressure control and relief capabilities to reduce the possibility of injury to humans and damage to equipment in the event of an overpressure situation. Such pressure control systems often use a pressure responsive member such as a buckling pin that mechanically collapses when subjected to a large increase in fluid pressure. Failure of the pressure responsive member allows a valve assembly to operate to establish an appropriate overpressure path for the fluid, such as by establishing a bypass path for the fluid or by shutting down a flow of the fluid.
While such systems typically operate to provide protection from overpressure conditions, there are also applications where it is desirable to detect and abate underpressure conditions as well. For example, a rupture in a pressurized pipeline or similar network can result in a drop in system pressure as the fluid escapes to the external environment. In such a case it is desirable to activate a valve assembly to establish a secondary path for the fluid (such as an upstream shutoff valve which halts further flow of the fluid) until the rupture condition can be remediated.
There is therefore a continued need for improvements in the art to provide a pressure control system that operates when a pressure of a pressurized fluid falls outside a selected operating range, both above the range in an overpressure context as well as below the range in an underpressure context. It is to such improvements that preferred embodiments of the present invention are generally directed.